Received October 10, 2021
Accepted April 21, 2022

Objective: It has been reported that transfer of embryos on day five has been associated with higher success rates, therefore our IVF clinics have started to extend embryo culture until blastocyst stage. This research aimed to compare success rates of day three vs day five embryo transfers. Materials and Methods: A total of 266 patients were included, all having undergone ICSI, with 221 patients having undergone day three embryo transfers, and 45 patients having undergone day five embryo transfers. Patients with more than five good quality embryos on day three were chosen to prolong the culture of embryos into day five. Results: There were no significant differences in patient characteristics, including basal hormone LH, FSH, Prolactin and Estradiol. Moreover, there were also no significant differences in total dosage of rFSH and duration of stimulation day. Final estradiol levels, number of follicles, retrieved oocytes, matured oocytes, fertilized oocytes and number of embryos were significantly higher in day five compared to day three embryo transfer groups. Number of embryos transferred on day three were significantly higher compared to day five. Neither group showed any significant differences in clinical pregnancy, implantation, multiple pregnancy or living birth rates. There were no differences in birth weights and lengths, head circumstances and Apgar Scores between both groups either in singleton or twin group. Conclusions: Transferring embryos at day three may provide the same benefits as day five embryo transfers to patients. However, more embryos were required to be transferred to achieve these comparable results.